Apparatus for cataphoretically treating a liquid suspension



May 11, 1948. H. F. FISHER 2,441,479

APPARATUS FOR CATAPHORETICALLY TREATING A LIQUID SUSPENSION OriginalFiled Dec. 22, 1941 A 1 E r 9 a i i ii a a t D a, 5; BS INVENTOR.

HAP/WON f. F/SHfE BY A Agent Patented May 11, 1948 APPARATUS FORCATAPHORETICALLY TREATING A LIQUID SUSPENSION Harmon F. Fisher, PaloAlto, Calif., assignor, by direct and mesne assignments, of one-half toUnion Oil Company of California, Los Angeles, Calif., a corporation ofCalifornia, and one-half to The Permanente Metals Corporation, acorporation of Delaware u Original application December 22, 1941, SerialN 0.

424,018. Divided and this application December 2'7, 1943, Serial No.515,792

1 Claim. 1

This application is a division of my application, Serial No. 424,018,filed December 22, 1941, for Separation of solids from liquids, andwhich is now Patent Number 2,376,535.

This invention relates to an apparatus for recovering finely dividedsolids capable of conducting current, such as metals and carbon, whichare held in suspension in non-conducting fluid, particularly in ahydrocarbon medium.

It is an object of the invention to provide a device for separatingtwo-phase systems consisting of one or more fine dividedcurrentconducting solids dispersed in a non-conducting liquid, to obtaina concentrated solid phase and a cleared liquid phase. One of theprimary objects of the invention is to provide means for concentratingmagnesium metal dust finely dispersed in a hydrocarbon medium.

Magnesium partly results in the form of dust in the refining, bydistillation, of crude electrolytically produced magnesium metal or ofmagnesium scrap, and particularly in the course of the recovery ofmetallic magnesium from oxidic magnesium compounds by thermic reduction,carried out at a temperature above the boiling point of metallicmagnesium and followed by cooling down the vapor to a temperature belowthe solidification point of metallic magnesium. Magnesium dust obtainedin one or the other of the above ways, particularly when partly in thestate of colloidally fine subdivision, is highly reactive with oxygenand nitrogen and. even spontaneously inflammable. It is old in the artto protect the dust against such unwanted conversions by immersing? thesame immediately after formation in a hydrocarbon oil medium or, in thecase of its resulting from shock chilling the vapor evolved in thecourse of thermic reduction of magnesium oxidecontaining startingmaterials, by using liquid hydrocarbons as the chilling medium proper.In any case the metallic magnesium is thus obtained in the state ofslurry in the hydrocarbon, containing the metal in such a finely dividedcondition that only a minor proportion can be separated by settling.Conventional methods of and the repelling electrode will be at apositive potential of about 5,000 to 100,000 volts depending upon gapspacing, the nature of the hydrocarbon liquid, etc., While thecollecting electrode will be grounded. When the particles are notsufficiently charged it may be necessary to have the repelling electrodeat a higher potential difierence above ground. Ionization in very smallamount from one electrode is picked up by the particles which becomecharged and are "carried to the collecting electrode of opposite signwhere they are collected in the form of a dense slurry. Static or batchapparatus may be utilized to obtain the desired effect, with periodicscraping or flushing off of the solids collected. However, I have foundthat a particularly suitable apparatus for continuous operation may beutilized which consists, as described in greater detail below and shownschematically in the drawing, of a rotating cylindrical drum partiallyimmersed in a bath of slurry.

separation, such as centrifuging, filtration, etc.,

The operation of the electrostatic separator may be observed in detailby reference to the drawing. Dirty feed enters the launder l, extendingthe length of the drum, and overflows into the annular space 2, betweenthe trough and the rotary drum 3. Drum 3 rotates countercurrent to theflow of the hydrocarbon slurry. Solid particles are drawn to the drumunder the influence of the electrostatic field and are deposited thereonin the form of a cake.

The hydrocarbon medium is progressively clarified as it'passes throughthe annular space and finally overflows as completely clear liquid freeof all suspended solids into a discharge launder 4-.

The cake 5 containing all of the solids removed from the slurry iscarried on the surface of the stream of inert gas, such as methane,natural gas;

hydrogen or carbon monoxide, through inlet 8,

over the cake 5 under a suitablehood 9; and The gas" out throughdischarge Opening l0. stream is preferably passed countercurrent to thedrum rotation in order to make fullest use of Countercurrent flow of thegashas been found particularly advantageous in; those cases where thehydrocarbon slurry'introavailable heat,

duced into launder I is at elevated temperatures. As a means ofintroducing the requiredheat to evaporate the hydrocarbon from. cake 5,-where this heat is not entirely furnished by the.1ho.ti slurryintroduced into launder I, I have found.

that several methods may conveniently be used. For example, the gasstream may be heated by external means (not shown) before introductionthrough opening 8, .or hood 9 may beexter'nally:

heated and heat passed to the gas stream by-radiation andconvection, orelectrical heating elements may be suspended in the gasstream'betweendrum 3 and hood 9. In this manner, anydesired proportion of solids andhydrocarbon may be obtained in the cake discharged into conveyor '1 bycontrolling the flow of gas andthe amount of heat employed.

In the practice of my invention I have found that-complete separation ofsuspended solids may be-obtained under a wide range of slurryconcentration and operating variables, such as drum size, speed of drumrotation, electrostatic potential, etc. Two unexpected phenomena havebeen discovered in practicing this invention, however,

namely that finer particles are easier to removeth'an larger and morethoroughly agglomerated particles, and also that higher throughput ofsolilds may be accomplished by using more dilute 4 feed of each slurrywas gradually increased to the maximum which could be maintained to givea clear solvent overflow free of all suspended solids. The followingdata were obtained:

i l 01 S l t D C k o 01 s in car 0 ven rum a e Slurry, Per 53 5Production, Production, Centby GaL/Hr. Lbs./Hr. Weight 7' l0 0. 41 0. 280. 89 5 l. 45 l. 27 l. 88 2% 2.78 2.19 2. 24

These data indicate the advantages to be obtained'whenusinga more diluteslurry. It is not alwaysipossible to obtain a slurry having the desired.concentration, and it is part of my invention todilute the slurryobtained with suitable clear solvent. The clear solvent may be obtainedby, circulation of clear solvent overflow from discharge 4=through pump1 I to the slurry line or directlyinto launder I.

In the foregoing discussion emphasis has been placedupon the separationof crude magnesium from a hydrocarbon slur ry. It is to beunderstoodthat my inventionis broad in its general application and maybe applied to the separation of any suspendedsolid material from aliquid hydrocarbon medium, provided only that theparticleshe chargechasin the caseof the magnesium, or be capable of having a suitable chargeplaced thereon. As hydrocarbons it is to be understood that anynormally-liquidhydrdcarbon or hydrocarbon mixture may be employed.

Iclaim:

Inan apparatus'forcataphoretically treating a liquid suspension, astationary concave trough of impermeable material to containthesuspensiontobe treated, a horizontall disposed rotatable drumofelectrical conducting material havingv its external surface partiallysubmerged in saidsuspension and close to the trough wall to define anannular passageway between the drum surface and theconcave surface ofsaid trough, means forv connecting .a'source of potential acrosssaiddrurnand said-trough for. energizing them into the annular spacethrough jets, not shown in the drawing.

As an example of the practice of myinvention, and also to show theefiect of feed dilution .the following experiment is illustrative. Aslurry of crude magnesium metal dust, containing some magnesium oxideand carbon, suspended inra. parafiinic hydrocarbon diluent having aboiling,

range of 300 to 400 F. was used for the experiment. The apparatus wassubstantially as de-, scribed above, with the collecting drum groundedand the lower electrode or trough at a positive electrostatic potentialof about 15,000 volts. The original feed contained 10% by weightof'solids,

and this was successively diluted with solvent to. give slurriescontaining 5% and 2% by weight of solids. Each of these feeds was thenpassed into the electrostatic separator while maintaininga constant drumspeed to give exposed surface gof 1917' square *feet per; hour; Therategof of opposite polarity, an inflow launder disposed along one edgeof the trough throughout substantially the entire length thereof todischarge said suspension into-saidpassageway for effecting auni-directionalfiow of saidsuspension in a circumferential direction.around the underside of the surface of saiddrum, a discharge launderalongthe. opposite edge of the trough toreceive clear phase. liquid fromsaid passageway, a cond'uitJeading-from. the discharge launder to theinflow launder and havin means therein for re-circulating a portion. ofsaid clear liquid through said passageway for reducing theconcentrationofsolids insaid'liquid suspension to thereby increase therate of deposition of solids insaidliquid. suspension onto the surface.of said drum, means for rotating said drum in a direction opposed to theflow of liquid in said annular passageway, said rotation of the drumserving to carry the solids deposited thereon from saidliquidfsuspension upwardly out of the liquid suspensionwhile stilladhering. ,to the drum, a hood enclosing the unsubmerged portion of thedrum and through which a stream of heatedgas is passed to flow over theunsubmerged surface of the drum in a direction opposedto the. directionof rotation ofjsaid drum for decreasing the plasticityof thesolid matterdeposited thereon, and means disposed. adjacent the discharge. launderand 5 above the liquid suspension for scraping said Number solid matterof decreased plasticity from the ex- 1,514,955 ternal surface of saiddrum. 1,719,984 HARMON F. FISHER. 1,855,809 5 2,031,210 REFERENCES CITED2 295 47 The following references are of record in the 2,300,233 file ofthis patent:

UNITED STATES PATENTS 10 Number Number Name Date 520,431

1,174,946 Illig Mar. 7, 1916 1,229,203 Schwerin June 5, 1917 Name DateDickey et a1 Nov. 11, 1924 Klein et a1 July 9, 1929 Sheppard et a1. Apr,26, 1932 Dillon et a1. Feb. 18, 1936 Ibison Sept, 18, 1942 Fisher Oct.27, 1942 FOREIGN PATENTS Country Date Great Britain 1940

